Dual safe fuze with spring preloader

ABSTRACT

The invention provides a novel dual safety fuze for a rocket-launched minelearing linear high explosive charge. The fuze comprises a tubular housing, having a forward section containing two booster charges for initiating the line charge, an intermediate section containing two electric delay detonators, a rotor containing two lead charges positioned between the forward and intermediate sections and a rearward section mounting two axial arming pins, which provide a first and second lock of the rotor in the safe position. A novel rotor spring assembly includes a rotatable shaft, whose one end is attached to a torsion spring for rotating the rotor and other end has a screw-like configuration, which is engaged by a fork-like driver mounted on the first arming pin. The torsion spring is not torqued when the rotor is in the safe position; but when the linear charge is deployed on the ground, the first firing pin is withdrawn from the rotor by the pull of the arresting cable, causing (1) the driver to rotate the screw/shaft and thereby preload the torsion spring and (2) the short across the two detonators to open and thus close the firing circuit. The operator then closes a firing control switch which (1) energizes the electrically piston-actuated second arming pin, thereby removing the second safety lock and releasing the rotor to rotate to the armed position, and (2) simultaneously energizes the delay detonators. On expiration of the delay period the detonators actuate and fire the line charge.

GOVERNMENT INTEREST

The invention described herein may be manufactured, used and licensed byor for the Government for governmental purposes without payment to me ofany royalty thereon.

BACKGROUND OF THE INVENTION

The U.S. Army presently employs a mine clearing system (USMCS) forproviding a cleared path in a battlefield. The system comprises a mineclearing line charge (MICLIC), which is dispensed at the battle zone bya rocket attached to its front end and has attached to its rear end afuze and an arresting cable, which in turn is anchored to a trailercontaining the line charge and other system components. At theconclusion of the rocket trajectory, the rocket, line charge, fuze andcable are stretched out in a long line on the ground, and the fuze hasbeen armed by the pull of the launcher cable on the arming pin so thatthe high explosives in the line charge can be initiated by detonators inthe fuze assembly.

The current M1134 fuze employed in the MICLIC system is a single safefuze, wherein the only safety is an arming pin, which holds the springloaded rotor out of line. This pin is retracted when it is pulled by anarresting cable of the line charge, thereby fully arming the fuze.

The current M1134 fuze does not meet present military standards for fuzedesign safety criteria because it lacks safety redundancy, has nofail-safe feature and requires stored rotor spring energy to arm. Inview of these safety deficiencies the current M1134 fuze is approved foruse with the MICLIC only for field assembly to the line charge. Storageof the MICLIC with the fuze assembled is not permitted.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a novel and improved fuze for explosivedevices, and particularly for line charge explosive systems. The fuze ofthe present invention is similar to the current M1134 fuze but inaddition contains several unique and key elements, whereby the safetydeficiencies of the present M1134 fuze are overcome, notably:

(1) a second; electrically activated arming pin, which provides a secondsafety feature; and

(2) a novel rotor spring assembly, which provides safety redundancy.

The novel rotor spring is installed in its free state and hence does nothave the stored energy which could inadvertently actuate the rotor andthereby arm the fuze, as in the present M1134 fuze. The novel rotorspring assembly comprises a torsion spring in combination with a screwelement and a driver element, such as a fork-like device, which engagesthe screw element and is mounted on the first arming pin, which in turnis pulled by the tension in the cable arrest of the line charge. In thisarrangement the linear motion of the arming pin is converted intorotation by the screw, which thereby winds up the rotor spring. At thesame time the first arming pin (the first safety lock) is withdrawn fromthe rotor it also opens the shorting switch, thereby closing theelectrical firing circuit of the electric detonators of the fuze.Thereafter, the second arming pin (the second safety lock) is actuatedby an electrical pulse and thereby withdrawn from the rotor, allowingthe rotor to rotate to the armed position for firing the line charge.

For a better understanding of the invention reference is made to thefollowing description taken in connection with the accompanyingdrawings.

LIST OF FIGURES

FIG. 1 is an exploded view of the present M-1134 fuze.

FIGS. 2 and 2A show a partial cutaway view of the present M-1134 fuze.

FIG. 3 shows an end plan view of internal parts of the present M-1134fuze.

FIG. 4 is an axial section view along the angled line X--X of FIG. 3, ofa fuze embodying the present invention.

FIG. 5 is an axial section view along the line C--C of FIG. 3, showingan electrically piston-actuated second arming pin of the fuze of thepresent invention.

FIG. 6 is a section view along line Y--Y of FIG. 4 showing a fork-likedriver.

FIG. 7 is an end plan view of portions of the fuze.

FIG. 8 is an axial section view along the angled line A--A of FIG. 7 ofa fuze showing another embodiment of the present invention.

FIG. 9 is an axial section along line C--C of FIG. 8.

FIG. 10 is a section view along line B--B of FIG. 8.

OPERATION OF THE MICLIC WITH THE PRESENT M1134 FUZE

After the MICLIC trailer is positioned, the rocket launcher is raisedand the shorting switch is closed, the operator rotates a firing controlswitch to the "ROCKET" position and repeatedly squeezes a 50 capblasting machine (not shown). An electrical pulse is thereby transmittedthrough the special purpose electric cable via the launcher safetyswitch assembly and the rocket motor connector to ignite the rocketmotor propellant, whereby the rocket propels the linear demolitioncharge across the selected area. As the last 10 feet of the arrestingcable leaves the charge container, the lanyard attached to the chargecontainer safety switch arm pulls the arm up and closes the electricalcircuit so that the linear detonation charge can be initiated. When therocket is in flight, the cable stretches, causing the arming wire topull the arming pin assembly in the fuze. The tension in the wirewithdraws the arming pin from the rotor, which releases the rotor torotate by spring action to the armed position, thereby aligning its leadcharges with the electric detonators and the booster charges. When thearming pin is pulled, the short across the two detonators is opened andthe arming circuit is closed.

After the line charge is deployed on the ground, the operator rotatesthe firing control switch indicator to the "CHARGE" position (not shown)and repeatedly squeezes the handles of the 50 cap blasting machine,whereby an electrical pulse is transmitted through the special purposeelectrical cable, the launcher safety switch assembly, the electricallead, the arresting cable fuze connector and the fuze. On reaching thefuze, the pulse detonates the electrical detonators, which in turndetonate the leads in the rotor, the boosters in the disk and thepenaerythritol tetranitrate (PETN) relays in the demolition charge fuzeconnector. Initiation of the PETN relays detonates the strands of thePETN detonating cord, which causes high order detonation of thecomposition C4 pellets in the linear demolition charge.

DESCRIPTION FO THE PRESENT M1134 FUZE

The present M1134 fuze is shown in FIGS. 1, 2 and 2A comprises a centertube enclosed in a crimped-on container, which is closed at the frontend by a thin aluminum wall. The center tube contains a threadedportion, which is secured to the wall end of the container by a circularnut, and an externally threaded portion, which is threaded into the openend of the container, and also contains two slots for meshing thedemolition charge connector with the fuze. The fuze is sealed againstthe entrance of moisture with two O-rings.

The center tube assembly contains (1) forward body section or diskhaving two passages containing booster pellets, (2) a rearward bodysection containing a capped electrical receptable, an arming pinassembly containing a firing switch and an electrical circuit for firingtwo electric detonators, 3) an intermediate body section with twopassages containing two electric detonators, and (4) a rotor positionedbetween the intermediate body section and the forward body section ordisk containing the electric detonators and the booster charges,respectfully. The arming pin assembly consists of an arming pindisconnect, a shear pin, a setscrew, a stop bar and an arming pin,wherein the shear pin prevents movement of the arming pin assembly untilthe arming wire tension is sufficient to shear it and retract the armingpin, which releases the rotor. The stop bar limits the rearward movementof the arming pin. The arming pin disconnect detaches from the fuze andis used to mechanically assemble the fuze with the arming wire connector(part of the arresting cable fuze connection). The stop bar and setscrew combine to prevent the arming pin to be completely retracted fromthe center tube. Also, the rotor cavity for receiving the arming pin isconical in shape so that if the fuze is armed but not fired, the armingpin disconnect can be reinserted into the center tube, which pushes thearming pin back into the conical cavity, thereby rotating the rotor tothe safe position. The fuze is about 31/2 inches in diameter and about43/4 inches long and weighs about 4 pounds.

When the arming pin is retracted to release the rotor, spring actionrotates the rotor until the two lead charges in the rotor, the twoelectric detonators in the intermediate body section and the twoboosters in the disk are aligned; at the same time the firing switch isclosed.

DESCRIPTION OF THE FUZE OF THE PRESENT INVENTION

One embodiment of a fuze of the present invention is shown in FIGS. 3-6,and another embodiment is illustrated in FIGS. 7-10.

The fuze of the present invention as shown in FIGS. 3 to 6 is generallysimilar to the M1134 fuze in that it contains a center tube assemblyenclosed in a cylindrical container EE. The center tube assemblycomprises a radial disk-like forward body portion R containing twobooster charges, a radial intermediate body section S containing twoelectric delay detonators, a rotor C, which is pivotably mounted betweenthe forward and intermediate body sections and contains two lead chargesand a first cavity V for receiving the first axial arming pin, and arearward body portion T, which contains the first arming pin assembly, adual electrical circuit including a switch assembly for two electricaldetonators and a capped electrical receptacle for the electric cable.

In addition, the fuze of the present invention has a second axial armingpin, which is mounted in the rearward body portion T and extends into asecond rotor cavity W, thereby providing a second safety lock. Thesecond arming pin is retracted by an electrically actuated piston F.Also, the stored energy rotor spring of the M1134 fuze is replaced by anovel rotor spring assembly, wherein the rotor spring is installed inthe free state, and hence does not possess the stored energy which couldinadvertently activate the rotor and thereby arm the fuze. As shown inFIG. 4, the rotor spring assembly comprises a rotatable axial shaft Lwhich is mounted in the intermediate body section S and possesses ahelical, screw-like section M at one end and a slot N at the other endfor anchoring a coiled torsion spring E containing an arm 0 for engagingand turning the rotor. The screw M is engaged by a fork-like driver Dfixedly mounted on the first arming pin. The driver is driven by therearward movement of the first arming pin produced by the pull of thearresting cable of the linear charge, whereby the linear motion of thearming pin is converted into rotation by the screw, which thereby windsup and preloads the rotor spring. Simultaneously, as this assembly movesthe first arming pin (the first safety lock) from the rotor, it opensthe shorting switch of the firing circuit. Also, the rotor has a lockinghole J for receiving a detent and locking ball G, which is biased by aspring SP contained in a hole HO by a screw SC in the intermediate bodysection S, and normally locks the rotor in the safe position.

The operation of the novel fuze in the MICLIC is as follows:

When the line charge is deployed on the ground, the cable arrest A pullsand retracts the first arming pin from the rotor C, thereby releasingthe first safety lock on the rotor, and also opens the shorting switchand closes a firing circuit for the electric detonator. At the same timethe fork D rides up the screw-shaft M and thereby winds up and torquesthe rotor spring E. At this point the line charge has been deployed onthe ground, and awaits the "charge" signal from the firing controlswitch. The operator then proceeds with the manual operating sequence bypressing the "charge" switch, thereby energizing the piston actuator F,which (1) retracts the second arming pin from the rotor and therebyreleases the second safety lock on the rotor, allowing the rotor torotate to the armed position, and (2) simultaneously energizes the delaydetonators H. When the second safety lock is thus removed, the preloadedrotor spring E overrides the detent and locking ball G, thereby aligningthe two lead charges in the rotor with the two delay detonators and thetwo booster charges. Following the expiration of the delay period (50 msec.) the detonator actuates and fires the line charge.

The fuze of the present invention retains the fuze form (diameter andlength) and the fuze interface with the line charge, and maintains thesystem sequence of operation.

Another embodiment of the rotor spring assembly of a fuze of thisinvention is shown in FIGS. 7-10, wherein the rigid screw/shaft portionshown in FIG. 4 is replaced by a pair of spring wires twisted into ascrew-like form which can be fabricated from one continuous length ofspring wire formed into a helix and welded at the end, as shown in FIG.8. In this construction the spring wire screw can function as thetorsion spring or primary elastic element, which serves to preload therotor, in which case the coiled rotor torsion spring shown in FIG. 4 canbe replaced by a rigid lever or arm for turning the rotor. Further,instead of the fork-like driver shape shown and described above, anydriver configuration which is mounted on the first arming pin and mateswith the screw-like configuration to rotate it, can be employed to windup and preload the rotor spring.

What is claimed is:
 1. In a fuze comprising a housing containing aforward body section having at least one passage containing a boostercharge, an intermediate body section having at least one passagecontaining an electric detonator, a rearward body section having mountedtherein a first slidable arming pin, and a rotor positioned between saidintermediate body section and said forward body section, said rotorhaving at least one passage containing a lead explosive charge and acavity for receiving the end of said arming pin to lock said rotor inthe safe position, said rotor passage being angularly displaced fromsaid electric detonator and booster charge passages when the rotor is inthe safe position and being aligned with said passages when said armingpin is withdrawn to release said rotor to rotate to the armed positionby means of a spring biasing means, wherein the improvementcomprises:(a) a second slidable arming pin mounted in said rearward bodysection, said pin being electrically actuated and extending into asecond cavity in said rotor to provide a second lock of the rotor in thesafe position; (b) a rotor spring assembly for rotating said rotor fromthe safe position to the armed position, comprising:(1) a rotatableshaft mounted in said intermediate body section having a screw-likeportion extending into a space between said intermediate and rearwardbody sections and a rearward portion having an arm-like member forengaging and rotating said rotor, wherein one of said screw-like portionand said arm-like member is a torsion spring and one is essentiallynon-elastic; and (2) a driver means mounted on said first arming pin forengaging and rotating said screw-like portion of said shaft by themovement of said first arming pin from said rotor and thereby wind upand preload said torsion spring,whereby said torsion spring means is ina free, non-preloaded mode when said first arming pin locks said rotorin the safe position, is in a preloaded mode when said first arming pinis withdrawn from said rotor, and rotates said rotor to the armedposition when said second arming pin is withdrawn from said second rotorcavity.
 2. A dual safe fuze with spring preloader suitable for a linecharge explosive system comprising a rocket attached to its forward endand a fuze and launcher cable attached to its rearward end, said fuzecontaining an electric detonator and requiring for the arming thereofthe pull of the launcher cable on a first arming pin in combination withthe electric actuation of a second arming pin therein, said electricdetonator and second arming pin being initiated by a pulse from anelectric cable connected thereto, which comprises:a housing meanscontaining a forward body section having at least one passage containinga booster charge, an intermediate body section containing at least onepassage containing an electric detonator, and a rearward body section; arotor means positioned between said forward and intermediate bodysections, said rotor means being rotatable between a safe position andan armed position and having at least one passage containing a leadexplosive charge which in the safe position is angularly displaced fromsaid passages containing said electric detonator and booster charge andis aligned with said passages in the armed position; and wherein saidrotor means contains a first cavity for receiving the end of a firstarming pin to provide a first lock of said rotor in the safe positionand a second cavity for receiving the end of a second arming pin forproviding a second lock of said rotor in the safe position; a firstarming pin assembly mounted in said rearward body section and containinga slidable arming pin into said first rotor cavity; a second arming pinassembly mounted in said rearward body section and containing anelectrically actuated slidable arming pin extending into said secondrotor cavity; a rotor spring assembly for rotating said rotor from thesafe position to the armed position comprising:(1) a rotatable shaftmeans mounted in said intermediate body section and having a screw-likeportion extending into a space between said intermediate and rearwardbody sections and having an arm-like member for engaging and rotatingsaid rotor, wherein one of said screw-like portion and said arm-likemember is a torsion spring and the other is essentially non-elastic, and(2) a driver means affixed to said first arming pin for engaging androtating said screw by movement of said first arming pin from said rotormeans and thereby wind up and preload said torsion spring,whereby saidtorsion spring is in a free, non-preloaded mode when said first armingpin locks said rotor in the safe position, is in a preloaded mode whensaid first arming pin is withdrawn from said rotor, and rotates saidrotor to the armed position when said second arming pin is withdrawnfrom said second rotor cavity.
 3. A fuze according to claim 1 or 2,wherein the screw-like portion is rigid and the arm-like member is atorsion spring.
 4. A fuze according to claim 1 or 2, wherein thescrew-like portion is a torsion spring and the arm-like member is arigid member.
 5. A fuze according to claim 1 or 2, wherein said drivermeans has a forklike configuration.
 6. A fuze according to claim 1 or 2,wherein the second arming pin and the electric detonator are actuatedsimultaneously and the detonator is a delay detonator.
 7. A fuzeaccording to claim 1 or 2, wherein said electric detonator is connectedto an electric firing circuit containing a shorting switch actuated bysaid first arming pin, whereby said switch is closed and the current isopen when said pin locks said rotor in the safe position, and is openedwhen said pin is withdrawn from said first rotor cavity, thereby closingthe firing circuit.
 8. A fuze according to claim 1 or 2, wherein saidintermediate body section has a cavity containing a spring-biased detentand locking ball and said rotor contains a cavity for receiving saidball for holding said rotor in the safe position, and wherein saidtorqued rotor spring overrides said detent and locking ball and rotatessaid rotor to the armed position when said second arming pin iswithdrawn from said second rotor cavity.
 9. A fuze according to claim 1or 2, wherein said intermediate body section, rotor means and forwardbody section each contain two of said passages containing said electricdetonators, lead charges and booster charges, respectively.